This invention relates to a screening plant for use in screening a bulk supply of raw material into at least one size range of screened material.
Screening plants are used typically in quarry environments, in order to separate crushed stone into different size ranges of screened material e.g. ballast, gravel, sand, and can be large scale semi-permanent installations. If a smaller scale screening operation is required, then a screening plant may be designed to be readily transportable e.g. on a low loader, or by being self-propelled, so as to be moved from one position to another on site, or from one site to another. Screening plants are also used in site clearance work, in which case the raw material supplied may be soil, clods, tree roots, broken bricks and concrete rubble.
There are many different types of screening plant available, and usually specifically designed for particular tasks. One existing design is known as a “trommel drum”, which is a rotating screening drum which has its axis of rotation extending nearly horizontally, although in fact extending gently downwardly from its upper loading end (through which the bulk material is supplied to the drum) to its lower discharge end from which material is discharged. The drum has screening apertures provided in the wall of the drum, through which screened material can pass. A trommel drum is a robust construction which is not expensive, is mechanically simple and therefore reliable, and is often chosen for particular situations.